/*
 * Copyright 2002-2006 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.commontemplate.util.coder;

/**
 * Utility class for JavaScript escaping. Escapes based on the JavaScript 1.5
 * recommendation.
 *
 * <p>
 * Reference: <a href="http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Guide:Literals#String_Literals"
 * > Core JavaScript 1.5 Guide </a>
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @since 1.1.1
 */
public class JavaScript {

    /**
     * Turn special characters into escaped characters conforming to JavaScript.
     * Handles complete character set defined in HTML 4.01 recommendation.
     *
     * @param input
     *            the input string
     * @return the escaped string
     */
    public static String encode(String input) {
        if (input == null) {
            return input;
        }

        StringBuffer filtered = new StringBuffer(input.length());
        char prevChar = '\u0000';
        char c;
        for (int i = 0; i < input.length(); i++) {
            c = input.charAt(i);
            if (c == '"') {
                filtered.append("\\\"");
            } else if (c == '\'') {
                filtered.append("\\'");
            } else if (c == '\\') {
                filtered.append("\\\\");
            } else if (c == '/') {
                filtered.append("\\/");
            } else if (c == '\t') {
                filtered.append("\\t");
            } else if (c == '\n') {
                if (prevChar != '\r') {
                    filtered.append("\\n");
                }
            } else if (c == '\r') {
                filtered.append("\\n");
            } else if (c == '\f') {
                filtered.append("\\f");
            } else {
                filtered.append(c);
            }
            prevChar = c;

        }
        return filtered.toString();
    }

}
